As a pathogen of public health significance, group A Streptococcus (GAS) infects 18.1 million people and leads to 500 000 deaths all over the world every year.GAS is often transmitted through respiratory droplets and contact with damaged skin.Children, the elderly and immunocompromised people are highly susceptible to GAS infection.Schools, kindergartens, hospitals, nursing homes and other densely populated areas are high-risk areas for GAS transmission.Prevention and control measures should highlight the improvement of living conditions and hand hygiene.Adherence to infection prevention and control measures should be emphasized in high-risk environments.In this paper, the risk factors, prevention and control strategies of GAS infection and transmission were summarized, so as to provide basis for the prevention and control of GAS.

Objective:To identify the epidemic types of Group A Streptococcus (GAS)causing scarlet fever, to compare the gene structure and variability of GAS with different emm types, and to elucidate the epidemiological pattern of scarlet fever pathogens in Shenzhen. Methods:Pharyngeal swab samples were collected and analyzed retrospectively from children diagnosed with scarlet fever in Shenzhen Children′s Hospital from January 1, 2016 to May 31, 2018.The GAS strains were preserved for emm genotyping analysis.The strains of representative emm types were selected for whole-genome sequencing.The genomic polymorphism of GAS strains was described by comparative genomic analysis.Moreover, a phylogenetic tree was constructed based on the whole genome core-gene single nucleotide polymorphisms(SNPs) to clarify the evolutionary relationship between strains.Data between groups were compared by Rank sum test. Results:Among 176 GAS isolates that caused scarlet fever in children, 8 emm types were detected.The most common genotype was emm12.0 and its subtype(108/176 strains, 61.4%), followed by emm1.0 and its subtype(53/176 strains, 30.1%). These two genotypes accounted for 91.5% of all isolates collected.Comparative genome analysis was made taking GCA-900984775 as a reference sequence, and the results showed that the genomes of GAS strains had high levels of SNP and insertion or deletion (InDel) polymorphisms.There were more SNPs in emm12.0 strains[183(163, 213)] than those in emm1.0 strains[63 (54, 75)], and the difference was statistically significant ( P<0.05). As for InDel, more insertions and deletions [4(3, 6), 8(6, 10)] were observed in emm12.0 strains than those [1(0, 2), 5(3, 7)] in emm1.0 strains.According to the phylogenetic tree built by taking MGAS5005 as the reference sequence based on the whole genome core-gene SNPs, 18 strains and reference strains formed two clades. Conclusions:The emm12.0 and emm1.0 types are the most common GAS strains leading to scarlet fever in children.There are differences in the genome composition of different GAS strains.The emm12.0 strains have higher genetic diversity.

Group A Streptococcus (GAS) is one of the most important pathogens leading to children deaths all over the world.Bacterial typing is the commonest approach to analyzing the epidemiological characteristics of pathogenic microorganisms.The emm typing is frequently adopted to study GAS.The emm cluster typing is a recently proposed typing method based on the amino acid sequence homology of M proteins and the ability to bind to the host serum protein.This typing system has been extensively used for epidemiological investigation, strain selection and vaccine deve-lopment in foreign countries.However, it has not been applied in China yet. emm typing is based on a small variable region of emm genes, while the emm cluster typing system defines GAS types according to nearly intact sequences of emm genes.Besides, the emm cluster grouping system is acquired directly by emm typing comparison, so it is simple and feasible.Furthermore, the emm cluster typing can provide more information regarding the functional and structural properties of M proteins in different emm types of GAS.In this review, the methods, principles and applications of the emm cluster typing system in GAS research were summarized, in order to promote its application in China.